class Solution {
    Map<Character,Set<Character>> edges = new HashMap<>();
    Map<Character,Integer> in=new HashMap<>();
    boolean check;
    public String alienOrder(String[] words) {
        for(String s:words){
            for(int i=0;i<s.length();i++){
                char ch=s.charAt(i);
                in.put(ch,0);
            }
…                    }
                    break;
                }
            }
            if(i==s2.length()&&i<s1.length()) check=true;
        } 
}